Module for optical information reader

ABSTRACT

A module for an optical information reader, wherein a light emitting unit ( 22 ), a collimator lens ( 23 ), a vibration mirror ( 31 ) for scanning, a condensing mirror ( 40 ), and a light receiving unit ( 50 ) are installed in a module casing ( 10 ) for modularization, and a lens-barrel hole ( 13   b ) opening at one end thereof and having an aperture ( 13   a ) formed at the tip face thereof is provided in the module casing ( 10 ), the collimator lens ( 23 ) is installed in the lens-barrel hole ( 13   b ) so as to come into contact with the tip bottom part thereof, and the light emitting unit ( 22 ) is press-fitted into the press-fit part ( 13   c ) of the lens-barrel hole in front of the collimator lens to form a laser beam generating part ( 20 ).

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/487,808 filed on Feb. 26, 2004,Pat. No. 7,206,109, which is anational stage application of PCT/JP02/08864 filed Sep. 2, 2002, whichclaims priority of JP H13-264556 (P) filed Aug. 31, 2001, which arehereby incorporated by reference in their entirety. Priority under 35U.S.C. §§120 and 121 is hereby claimed for the benefit of the filingdate of U.S. patent application Ser. No. 10/487,808.

TECHNICAL FIELD

The present invention relates to a module for an optical informationreader in which primary components in the optical information readerthat optically reads information of an object to be read such as a barcode or the like having portions with different light reflectances byscanning it with a light beam and outputs code data indicating theinformation of the object to be read are installed in a common modulecasing.

BACKGROUND TECHNOLOGY

As optical information readers, bar code readers that read bar codesindicating information such as names, prices, and so on of products arein wide use in the distribution industry and the retail industry.

These bar code readers are broadly classified into a hand type and afixed type, and further the hand type includes a pen type, a touch type,and a light beam scanning type (laser type). The fixed type is a lightbeam scanning type designed to be capable of scanning in a plurality ofdirections.

Among these readers, an optical information reader that is a target ofthe invention is one corresponding to the hand type bar code reader bythe light beam scanning type.

The bar code reader of the light beam scanning type brings laser lightgenerated by a light source such as laser diode (semiconductor laser) orthe like into beam form, deflects the light beam by a reflecting mirrorto cause it to impinge on a bar code, rotates or vibrates (oscillates)the reflecting mirror to scan the bar code in such a manner that thelight beam traverses the bar code.

Then, reflected light from the bar code is condensed and received by areceiving sensor to be converted into an electric signal. The electricsignal is subjected to A/D conversion and encoded, and outputted as barcode read information.

Typical light beam scanning mechanisms used in such a conventionaloptical information reader of the light beam scanning type are one usinga polygon mirror and a rotary drive motor and one using a single facemirror and a galvano motor.

Each of these light beam scanning mechanisms, however, is difficult tobe reduced in dimensions in its height direction (direction of arotation shaft) and a direction orthogonal thereto because the polygonmirror and the rotary drive motor or the single face mirror and thegalvano motor are separated bodies which are coupled to each other by arotation shaft directly or via a reduction mechanism.

Hence, to solve such a disadvantage of the conventional light beamscanning mechanism, the present inventor et al. provided vibrationmirror type scanner that is reduced in size by integrating a reflectingmirror, a movable magnet, and a rotation shaft (see JP H7-261109 and JPH8-129600).

Whereas, in the market thereafter, for further enhancement ofconvenience of such an optical information reader, further expansion ofuses, and creation of new type of usage, it is demanded to furtherreduce in size, thickness, and weight a vibration mirror scanning partforming a core part of the reader. Therefore, the present inventor etal. further develop and provide for the market a vibration mirror typescanner intended to achieve the aforementioned reduction in size,thickness, and weight and coping with the need for further improvementin scanning frequency and a maximum scanning angle of a light beam andthe need for correction control of scanning characteristics andtemperature characteristics of the beam (see JP H11-213086).

Further, as a technique on the reduction in size, thickness, and weightof the optical information reader that is the demand of the market,there provided is a one-piece optical assembly for an optical scanner(see JP H11-326805), a retroreflection scanning module for anelectro-optic reader (see JP 2000-298242), or the like as one in which alaser diode, a light detector, various optical elements, and so on arepositioned and accommodated in a molded resin member for assembly ormodularization.

On the other hand, in the optical information reader of the light beamcanning type, it is necessary that a light emitting unit with a laserdiode as a light source, a collimator lens for bringing laser lightemitted by the laser diode into a parallel luminous flux, and a memberprovided with an aperture for emitting the resulting laser light in athin beam are positioned and secured in a lens-barrel with their opticalaxes coinciding one another.

Collimator lenses are not uniform in size (for example, diameter) andhave some error, and therefore it is necessary to give slight room tothe inner diameter of the lens-barrel so that all of the collimatorlenses can be fitted thereinto. Further, there is a small but real errorin the positional accuracy of the laser diode in the light emittingunit. To correct these errors, means for correcting the optical axis isrequired.

Therefore, for example, a structure shown in FIG. 31 has been employedas the structure of a conventional laser beam generating part.Specifically, a flange for optical axis adjustment 103 is adhered to alight emitting unit 102, a light emitting part 102 a of the lightemitting unit 102 is inserted into a lens-barrel 101 provided in acasing whose illustration is omitted from one end face side thereof, andthe flange for optical axis adjustment 103 is secured to the lens-barrel101 with screws 104. Further, an O-ring 105 and a collimator lens 106are inserted into the lens-barrel 101 from the other end face side, andan aperture ring 107 with an aperture 108 formed at the center isscrewed into the lens-barrel 101 so that the collimator lens 106 issandwiched and secured between the aperture ring 107 and a flange part101 a in the lens-barrel 101 with the O-ring 105 giving preload thereto.

In this event, the screw-in amount of the aperture ring 107 is adjustedso that a light emitting point of the light emitting unit 102 is at aposition slightly farther than a focus point of the collimator lens 106.Further, the attachment position in the diameter direction of the lightemitting unit 102 by the flange for optical axis adjustment 103 and thescrews 104 is adjusted so that the optical axes of the collimator lens106 and light emitting unit 102 coincide with each other. For thatpurpose, the inner diameter of a screw insertion hole 103 a of theflange for optical axis adjustment 103 is made larger than the outerdiameter of the screw 104, thereby enabling fine adjustment of theattachment position in the diameter direction of the light emitting unit102.

However, since the demanded accuracy of attachment of the light emittingunit and collimator lens in the laser beam generating part is very high,it is difficult to achieve the demanded accuracy of optical axisadjustment and focus adjustment in this kind of conventional attachmentstructure. In addition, as shown in FIG. 31, the flange for optical axisadjustment 103 for adjusting the optical axis of a laser is adhered tothe rear part of the light emitting unit 102 and both are screwed to theend face of the lens-barrel 101, and therefore the number of componentsnecessarily increases and screwed parts occupy a large capacity, leadingto an obstacle to a reduction in size and price.

Hence, there also is a reader in which the optical axis adjustmentmechanism is omitted to reduce the size and the number of components ofthe laser beam generating part. This, however, increases variations inthe optical axis, resulting in variations of about ±4° in the scandirection.

Besides, enhanced reading accuracy of the bar code symbol might causewrong information to be also read. There can be as well printingnonuniformity of the bar code symbol and ink scattered to spaces in thebar code symbol as blurred black bars and so on. Further, optical noiseis also caused by a speckle pattern (grain-like flicker occurring when alaser beam is applied) generated by a laser beam on bar code papersurface. There is a problem that even though the above-described defectsare small enough not be recognized by the naked eye, a reader withenhanced reading accuracy may catch them as signals.

It is difficult to avoid such optical noise in the optical informationreader of the scanning type by a laser beam, but it is desirable todecrease its influence as much as possible.

Besides, in a module for an optical information reader in recent years,an LSI (large-scale integration circuit) is used to process an electricsignal made from reflected light from a bar code detected by a lightreceiving sensor or to control respective parts in the module.

Typically, this LSI is mounted on a circuit board that is to be attachedto the top or the side of the main body of the module.

However, depending on the use environment of the optical informationreader, various kinds of electronic devices are often used, and there isa serious problem that the above-described LSI is affected by theelectromagnetic wave noise caused by these devices. In addition, sincemobile phones have become widespread and are used not only for a simpletelephone function but also as information terminals, existence of aplurality of mobile phones in a work area is not uncommon, and thereforeit is also necessary to consider the influence of electromagnetic wavenoise caused by those phones.

Hence, to avoid those noises, the LSI mounted on the top or the side ofthe module main body is covered with a metal plate for shield in theprior art.

However, the module becomes bulky by the volume of the metal plate inaddition to the thickness of the LSI, leading to one of the obstacles toa reduction in size. In addition, the need for the metal plate increasesthe number of components as well as the number of attachment stepsthereof.

It is an object of the invention to modularize the primary part of anoptical information reader of the light beam scanning type, simplify thestructures of attachment parts of a light emitting unit and a collimatorlens, and enable read with highly accuracy, so as to reduce the size andprice of the optical information reader. It is another object toeliminate most of the variation with time and the influence of theabove-described optical noise and electromagnetic wave noise, so as toenable information read with high accuracy for a long time.

DISCLOSURE OF THE INVENTION

To attain the above-described objects, the present invention ischaracterized in that a module for an optical information reader inwhich at least a light emitting unit with a laser diode as a lightsource, a collimator lens, a vibration mirror for scanning, a condensingmirror or a condensing lens, and a light receiving unit are installed ina module casing for modularization, is configured as follows.

Specifically, the module casing is provided with a lens-barrel holehaving an opening at one end face thereof and an aperture formed at atip face thereof and having a press-fit part, provided between theopening and the tip face, into which the light emitting unit is to bepress-fitted, the collimator lens is adhered to a tip bottom part of thelens-barrel hole, and the light emitting unit is press-fitted into thepress-fit part in order to position a light emitting point of the laserdiode slightly farther than a focus point of the collimator lens, tothereby form a laser beam generating part.

It is preferable that to configure the lens-barrel hole such that aninner peripheral face of the press-fit part is a cylindrical face withan inner diameter almost the same as an outer diameter of the lightemitting unit that is to be press-fitted thereinto, and an innerperipheral face near the opening is a tapered face gradually increasingin inner diameter toward the opening.

Further, it is preferable that a cylindrical lens assembly comprising aplurality of cylindrical lens pieces integrally joined is providedbetween the light emitting unit and the vibration mirror, and each ofthe plurality of cylindrical lens pieces has one face that forms acylindrical concave surface having the same curvature and a differentcenter position and another face that is a flat surface orthogonal to anoptical axis, so that one of the plurality of cylindrical lens pieces isselected and inserted into a passing position of a laser beam generatedby the light emitting unit to enable adjustment of an optical axis ofthe laser beam.

Alternatively, each of the plurality of cylindrical lens pieces formingthe cylindrical lens assembly has one face that forms a cylindricalconcave surface having the same curvature and the same center positionand another face that is a flat surface tilting at a different angle toa curve direction of the cylindrical concave surface with respect to adirection orthogonal to an optical axis, so that one of the plurality ofcylindrical lens pieces is selected and inserted into a passing positionof a laser beam generated by the light emitting unit to enableadjustment of an optical axis of the laser beam.

In these modules for optical information readers, it is possible thatthe plurality of cylindrical lens pieces forming the cylindrical lensassembly are four or more triangular cylindrical lens pieces, and thecylindrical lens pieces are joined such that two sides of each of thecylindrical lens pieces are adjacent to two sides of other cylindricallens pieces to form the cylindrical lens assembly in one polygon.

Further, it is also adoptable that the plurality of cylindrical lenspieces are four square cylindrical lens pieces, and the cylindrical lenspieces are joined such that two orthogonal sides of each of thecylindrical lens pieces are adjacent to two sides of other cylindricallens pieces to form the cylindrical lens assembly in one square.

Alternatively, it is also possible that each of the plurality ofcylindrical lens pieces is a circular cylindrical lens piece, and thecylindrical lens pieces are joined and held on one plane using a supportmember to form the one cylindrical lens assembly.

Furthermore, the module casing is made of metal and formed with an LSIaccommodating recessed part, a circuit board with a shield layer and anLSI mounted thereon for forming a circuit for signal processing andcontrol is attached to an open face of the module casing with the LSIaccommodated in the LSI accommodating recessed part, and the LSI isshielded with the metal face of the module casing and the shield layerof the circuit board, whereby the LSI can be completely prevented frombeing affected by electromagnetic wave noise.

Combination of the above configurations can provide a more desirablemodule for an optical information reader.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view showing placement of components except a circuitboard in a module of an embodiment of a module for an opticalinformation reader according to the invention;

FIG. 2 is a front view showing the module of the same together with alongitudinal cross section of a module casing;

FIG. 3 is a perspective view showing the external appearance only of themodule casing of the same;

FIG. 4 is a cross-sectional view taken along a line IV-IV in FIG. 3showing a state in which a circuit board is attached to the top face ofthe module casing;

FIG. 5 is a cross-sectional view showing a state in which a lightemitting unit is press-fitted using a jig into a lens-barrel hole in themodule casing;

FIG. 6 is an enlarged cross-sectional view showing a state in which theinstallation of the light emitting unit and a collimator lens into thelens-barrel hole has been completed;

FIG. 7 is a front view of a cylindrical lens assembly 60 shown in FIG.1;

FIG. 8 is a cross-sectional view taken along a line VIII-VIII in FIG. 7;

FIG. 9 is a schematic view showing an appearance of a laser beam passingthrough one cylindrical lens;

FIG. 10 is schematic view when one of cylindrical lens pieces of acylindrical lens assembly is selected to perform optical axis adjustmentof a laser beam;

FIG. 11 is a schematic view when front and rear faces of the cylindricallens assembly are reversed, and one of cylindrical lens pieces of acylindrical lens assembly is selected to perform optical axis adjustmentof a laser beam;

FIG. 12 is a view schematically showing seven kinds of selection statesprovided by a cylindrical lens assembly;

FIG. 13 is an explanatory view showing an example of optical axisadjustment of a laser beam actually emitted from a laser beam generatingpart;

FIG. 14 is a plan view of a cylindrical lens assembly composed fourright triangular cylindrical lens pieces;

FIG. 15 is an explanatory view showing changes of the optical axes oflaser beams passing through the cylindrical lens pieces of the same;

FIG. 16 is an explanatory view showing changes of the optical axes oflaser beams passing through the cylindrical lens pieces when thecylindrical lens pieces are different in shape from those shown in FIG.15;

FIG. 17 is a plan view showing an example of a hexagonal cylindricallens assembly composed of six triangular cylindrical lens pieces;

FIG. 18 is a plan view showing an example of a square cylindrical lensassembly composed of four square cylindrical lens pieces;

FIG. 19 is a plan view showing an example of a square cylindrical lensassembly composed of four circular cylindrical lens pieces and a supportmember thereof;

FIG. 20 is a plan view of the vibration mirror driver shown in FIG. 1;

FIG. 21 is a side view of the same;

FIG. 22 is a cross-sectional view of a vibration mirror holding memberand a member fixed thereto of the same;

FIG. 23 is a view provided for explaining the magnetic flux distributionbetween a movable magnet and a yoke shown in FIG. 20, a schematic viewof a state where a movable magnet 33 stands still;

FIG. 24 is a schematic view showing a case in which the movable magnetis rotated 13.5 degrees of the same;

FIG. 25 is a schematic view showing a case in which the movable magnetis rotated −13.5 degrees of the same;

FIG. 26 is a diagram showing waveforms of a timing signal for turningthe vibration mirror in FIG. 20 right and left and a coil current;

FIG. 27 is a simulation waveform diagram of a detection signal when anelectromagnetic wave noise at about 30 KHz is superimposed using amodule according to the invention;

FIG. 28 is a simulation waveform diagram of a detection signal when anelectromagnetic wave noise at about 30 KHz is superimposed using aconventional module;

FIG. 29 is a simulation waveform diagram of a detection signal when amobile phone is used near the module according to the invention;

FIG. 30 is a simulation waveform diagram of a detection signal when amobile phone is used near the conventional module; and

FIG. 31 is a cross-sectional view showing a structure example of a laserbeam generating part in a conventional optical information reader.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of a module for an optical information reader according tothe invention will specifically be descried below with reference to thedrawings.

FIG. 1 is a plan view showing placement of components except a circuitboard in the module for the optical information reader, in which onlythe outline of a module casing is shown by an imaginary line. FIG. 2 isa front view of the same, showing the longitudinal cross section of themodule casing. FIG. 3 is a perspective view showing the externalappearance only of the module casing, and FIG. 4 is a cross-sectionalview showing the cross-sectional view along a line IV-IV in FIG. 3 in astate in which the circuit board is attached to the top face of themodule casing.

The module for the optical information reader (hereinafter referred toonly as a “module”) 1 is composed of, as shown in FIG. 1 and FIG. 2, amodule casing 10, and a laser beam generating part 20, a vibrationmirror driver 30, a concave condensing mirror 40, a light receiving unit50, a cylindrical lens assembly 60 for optical axis correction(hereinafter abbreviated as a “CR lens assembly”), and a circuit board70 to be attached to the top face of the module casing 10, which areinstalled in the module casing 10.

The module casing 10 is formed of a zinc alloy called ZDC2 by a die castprocess, and has a size of 14 mm in depth (D), 28 mm in width (W), and 8mm in height (H) as the whole outer shape. In place of the zinc alloy,aluminum or aluminum alloys, or magnesium alloys may be used. Note thatthe reason why the casing is formed of such metals is to obtainsufficient accuracy and strength and to achieve a later-described shieldeffect for LSI. When the achievement of the shield effect is separatelyconsidered, the casing may be formed of a resin such as reinforcedplastic.

Further, as shown in FIG. 3, a sidewall part 12 surrounding a bottomface part 11 and its periphery, a laser beam generating partaccommodation part 13, an LSI accommodating recessed part 14, alens/mirror attachment part 15, a vibration mirror driver attachmentpart 16, a light receiving unit attachment part 17, and so on, areformed in this example. On the bottom face part 11 at the vibrationmirror driver attachment part 16, a boss 18 is formed so that a supportshaft 34 of a vibration mirror is to be implanted therein. The frontface of the sidewall part 12 corresponding to the vibration mirrordriver attachment part 16 is open to form an opening part 19 foremission/incidence of a laser beam. The laser beam generating partaccommodation part 13 has an aperture 13 a for emission of a laser beamformed in the inner face.

The laser beam generating part 20 is composed of a light emitting unit22 including a laser diode 21, a collimator lens 23, and an O-ring 24,which are secured in a lens-barrel hole 13 b formed as shown in FIG. 2at the laser beam generating part accommodation part 13 of the modulecasing 10. The details of this attachment structure and attachmentmethod will be described later. The light emitting unit 22 has threeterminals 22 a projecting rearward (only two are viewed since two of thethree terminals overlap each other in the drawing).

The vibration mirror driver 30 is composed of, as shown in FIG. 1, avibration mirror 31 made of metal, resin, or glass for scanning a laserbeam, a vibration mirror holding member 32 made of resin with thevibration mirror 31 fixed to the front face part thereof, a movablemagnet (permanent magnet) 33 fixed to the rear face side of thevibration mirror holding member 32, the support shaft 34 in a pin shapefor turnably supporting the vibration mirror holding member 32, and acoil unit 35 located in such a manner as to be opposed and parallel toand spaced from the movable magnet 33. In the coil unit 35, a yoke 37 isprovided through a coil 36 in a vertical direction to a windingdirection of the coil 36.

These are attached to the vibration mirror driver attachment part 16 ofthe module casing 10. Then, the movable magnet 33 and the coil unit 35are operated to vibrate the vibration mirror holding member 32 and thevibration mirror 31 fixed thereto in a seesaw manner as shown by arrowsA and B. The configuration and operation will be described later.

At the lens/mirror attachment part 15 of the module casing 10, the CRlens assembly 60 is fixed to the outside of the face formed with theaperture 13 a of the laser beam generating part accommodation part 13,and the concave condensing mirror 40 is obliquely fixed in such a manneras to be spaced from the CR lens assembly 60 and opposed to thevibration mirror 31 and the light receiving unit 50. In the central partof the condensing mirror 40, a square through hole 41 is formed forallowing a laser beam to pass therethrough. The configuration andoperation of the CR lens assembly 60 for optical axis correction will bedescribed later in detail.

The light receiving unit 50 has a light receiving element 51 such as aphotodiode or the like and is installed at the light receiving unitattachment part 17 of the module casing 10, and its two terminals 52 areconnected to the circuit board 70.

The function of the module 1 thus configured will be described mainlyusing FIG. 1.

The laser beam generating part 20 generates a laser beam by lightemission of the laser diode that is the light source in the lightemitting unit 22, brings the laser beam into a parallel luminous flux bythe collimator lens 23 and emits it through the aperture 13 a as a laserbeam L1 show by a solid line.

The laser beam L1 is subjected to correction of deviation of its opticalaxis and brought into an elliptical luminous flux extended in thevertical direction by the CR lens assembly 60, passes through thethrough hole 41 in the condensing mirror 40 to reach the vibrationmirror 31, and is reflected by vibration of the vibration mirror 31within a predetermined angle range around 90° to be emitted from theopening part 19 to the outside. The laser beam irradiates a not-shownbar code symbol.

The bar code symbol forms a plurality of black and white verticalstripes each having a predetermined width that is determined bystandards as well known. These are called black bars and spaces. By theblack bars and spaces, light having a different reflectance isreflected.

A beam L2 reflected from the bar code symbol passes through the openingpart 19 again and is incident on and reflected by the vibration mirror31. The reflected light is condensed by the condensing mirror 40. Inthis event, the vibration mirror 31 vibrates due to a magnetic forcegenerated between the coil unit 35 and the movable magnet 33, and thusallows reflected light within a wide range from the bar code symbol tobe incident thereon and sent to the condensing mirror 40. All the lightcondensed by the condensing mirror 40 is then sent to the lightreceiving element 51 of the light receiving unit 50 (traces of the beamsare shown by broken lines).

The light receiving unit 50 outputs an electric signal corresponding tothe intensity of light received by the light receiving element 51 andsends the electric signal to the circuit board 70 through the terminals52. The electric signal is subjected there to A/D conversion and thendigital signal processing, whereby read data of the bar code symbol canbe obtained.

On the circuit board 70, a not-shown required wiring pattern is formed,and various electronic components 73 in chip forms are attached as shownin FIG. 4, and, on the rear side thereof, an LSI 71 for serving acentral function such as signal processing and control is installed.

The circuit board 70 is then attached and fixed to the top face of themodule casing 10 with a plurality of screws 74 to thereby serve also asa top cover of this module. In this event, the LSI 71 is accommodated,not projecting to the outside, in the LSI accommodating recessed part 14of the module casing 10. In addition, the LSI 71 is accommodated in therecessed part 14 of the module casing 10 made of metal to be surroundedby metal faces at least at four outer peripheral faces for desirableshielding, and thus can be prevented from being affected byelectromagnetic wave noise generated by other electronic equipment,mobile phone, and so on. This effect will be described later in detail.

This module for the optical information reader 1 can be installed in anot-shown case together with a power source and so on to therebycomplete with ease an optical information reader such as a small handtype bar code reader or the like.

Next, the attachment structure and attachment method of the lightemitting unit 22 and the collimator lens 23 in the laser beam generatingpart 20 according to this embodiment will be described with reference toFIG. 5 and FIG. 6.

FIG. 5 is a cross-sectional view showing a state in which the lightemitting unit is press-fitted using a jig into the lens-barrel holeprovided in the module casing, and FIG. 6 is an enlarged cross-sectionalview showing a state in which the installation of the light emittingunit and the collimator lens into the lens-barrel hole has beencompleted.

A press-fitting jig 80 shown in FIG. 5 is a device capable ofpress-fitting a member with a physical pressure. This press-fitting jig80 comprises a first securing member 81, a second securing member 82, apressure shaft 83, a handle 84 with a pressing member 85 integrallyfixed thereto with bolts 86, and so on.

The first securing member 81 is provided with a module setting recessedpart 81 a into which the module casing 10 can be inserted to be heldtherein. The central part of the second securing member 82 is providedwith a shaft guide hole 82 a into which the pressure shaft 83 isinserted to be movable in its axial direction. There is a femalethreaded hole 82 b therearound. The pressing member 85 is formed with amale thread 85 b at the outer periphery that is designed to be screwedinto the female threaded hole 82 b of the second securing member 82.

The first securing member 81 and the second securing member 82 areintegrally fixed to each other with a plurality of bolts 87.

On the other hand, in the laser beam generating part accommodation part13 of the module casing 10, the lens-barrel hole 13 b is formed, asshown in FIG. 6, in which the light emitting unit 22 and the collimatorlens 23 should be accommodated.

The lens-barrel hole 13 b has an opening at one end face of the modulecasing 10 and the aperture 13 a formed at the tip face thereof and has,between the opening and the tip face, a press-fit part 13 c into whichthe light emitting unit 22 is to be inserted. The inner peripheral faceof the press-fit part 13 c is a cylindrical face with an inner diameterslightly smaller than the outer diameter of the light emitting unit 22that is to be inserted thereinto, and a tapered press-fit guide part 13e is formed near the opening of the lens-barrel hole 13 b that has aninner peripheral face gradually increasing in inner diameter toward theopening.

The press-fit part 13 c of the lens-barrel hole 13 b is formed into atapered face that is slightly inclined by several microns such that theinner diameter on the front side is slightly large and decreases littleby little toward the bottom side, which can also facilitatepress-fitting of the light emitting unit 22.

To a stepped part 13 d at the tip bottom part of the lens-barrel hole 13b, the collimator lens 23 is sealed and adhered with a UV adhesive.Thereafter, the light emitting unit 22 is lightly inserted together withthe dustproof O-ring 24 into the tapered press-fit guide part 13 e.

After the module casing 10 in this state is inserted into and supportedby the module setting recessed part 81 a of the first securing member 81of the press-fitting jig 80 as shown in FIG. 5, the tip part of thepressure shaft 83 is permitted to abut on the rear end face of the lightemitting unit 22, and the pressing member 85 is screwed into the secondsecuring member 82 with the handle 84 grasped. Note that theillustration of the collimator lens 23 is omitted in FIG. 5 forconvenience of illustration.

With rotation of the handle 84, the pressure shaft 83 is pressed by thepressing member 85 to move leftward in FIG. 5, so that its tip partpresses the rear end face of the light emitting unit 22 to press-fit thelight emitting unit 22 to the bottom side of the lens-barrel hole 13 b.The pressure shaft 83 is in the shape of a hollow cylinder, and thusallows the terminals 22 a projecting from the rear end face of the lightemitting unit 22 to escape into the hollow and connect to lead wires, sothat the laser diode 21 in the light emitting unit 22 can be suppliedwith power from the outside for light emission.

At this moment, since the vibration mirror 31 is not installed yet inthe module casing 10, a focusing mirror 8 is inserted to reflect thelaser beam L1 emitted via the collimator lens 23 and the aperture 13 aand guide it to the outside, the light emitting unit 22 is positioned ata point where a light emitting point of the installed laser diodereaches a position that is slightly farther than a focus point of thecollimator lens 23, while accurately measuring the diameter of the laserbeam L1 using a laser beam measuring device (not shown), and thenoperation of the handle 84 is stopped. At this point of time, theinstallation of the light emitting unit 22 is completed. The laser beamemitted from the laser diode and passes through the collimator lens 23in this event has a profile that slightly converges from a parallelluminous flux. The focusing mirror 8 is removed after the adjustment.

In this state, the dustproof O-ring 24 is sandwiched between the steppedpart of the light emitting unit 22 and the tapered inner wall face ofthe lens-barrel hole 13 b to be slightly compressed to seal the space onthe collimator lens 23 side, thereby preventing entrance of dust.

The attachment structure and attachment method of the light emittingunit 22 and the collimator lens 23 in the laser beam generating part 20are designed as described above, whereby the number of components in useis greatly reduced from that in the prior art, and the space forscrewing also becomes unnecessary, resulting in a great contribution toa reduction in cost and size of the optical information reader.

Specifically, six components and two screws are used in the conventionalstructure shown in FIG. 31, but, according to the invention, it becomespossible to configure the structure through use of four componentsincluding the laser beam generating part accommodation part 13 of themodule casing 10 as shown in FIG. 6.

Next, the CR lens assembly 60 for optical axis adjustment shown in FIG.1 will be described in detail with reference to FIG. 7 to FIG. 19.

The diameter of the collimator lens 23 for use in the laser beamgenerating part 20 shown in FIG. 1 has a difference about 0.02 mmbetween the maximum and the minimum generated in the manufacturingprocess. To fit every one of these lenses into the lens-barrel hole 13 bof the module casing 10, it is necessary to provide a clearance betweenthe collimator lens 23 and the module casing 10. The provision of theclearance results in the collimator lens 23 having an optical axisdeviation of about 0.0205 mm. Further, the positional accuracy of thelight emitting point of the laser diode of the light emitting unit 22 istypically ±0.080 mm. Therefore, the maximum angle of tilt of the opticalaxis in the laser beam generating part 20 can be obtained by thefollowing equation.Tan⁻¹[(0.0205+0.08+0.005)/2.4]=2.517°

It should be noted that, in this equation, “0.005” is the amount of coredeviation (±0.005 mm) between the fitting part of the collimator lens inthe lens-barrel hole 13 b and the press-fit part 13 c of the lightemitting unit, and “2.4” is a focal distance (mm) of the collimator lensproduced by a glass mold.

Besides, in the vibration mirror driver 30, where the axis deviation dueto the support shaft 34 into which the vibration mirror holding member32 is fitted is 0.4°, and the axis deviation due to a maximum tilt ofadherence of the vibration mirror 31 is 0.4°, the tilt of the opticalaxis at the vibration mirror driver 30 is,0.4+0.4=0.8°Accordingly, the maximum tilt of the optical axis as a whole is 3.317°.

It is preferable to correct the tilt to make the optical axis straightand emit the beam from the module casing 10. In this embodiment, theoptical axis correction is performed through use of the CR lens assembly60. Further, the concave surface of the CR lens assembly 60 is used toemit a circular laser beam generated by the laser beam generating part20 as an elliptic beam longer than it is wide.

FIG. 7 is a front view of the CR lens assembly 60 shown in FIG. 1, andFIG. 8 is a cross-sectional view taken along a line VIII-VIII in FIG. 7.

As for the CR lens assembly 60, a plurality of cylindrical lens pieces(hereinafter, abbreviated as “CR lens pieces”) are integrally joined toform one CR lens assembly 60. In the example shown in FIG. 7, four righttriangular CR lens pieces 3 a, 3 b, 3 c, and 3 d are joined in a mannerthat two sides of each one are adjacent to two sides of others to formone square CR lens assembly.

Each of the four CR lens pieces 3 a, 3 b, 3 c, and 3 d has one face 60 a(a face on the right side in FIG. 8) that forms a cylindrical concavesurface (round surface: R surface) having the same curvature and adifferent center position as shown in FIG. 7, and another face 60 b (aface on the left side in FIG. 8) that is a flat surface orthogonal tothe optical axis (coincident with a mechanical axis 61 in the example inFIG. 8).

Further, these CR lens pieces 3 a, 3 b, 3 c, and 3 d can be produced bycutting them out of one cylindrical lens. Alternatively, they are cutout of cylindrical lenses having R surfaces with the same curvature,which eliminates the necessity to cut them out of the same onecylindrical lens.

In the CR lens piece 3 a, the offset of the center position of the Rsurface from the mechanical axis 61 passing through the center of the CRlens assembly 60 shown in FIG. 7 is 0, the center position of the CRlens piece 3 a is a position that includes the center of the CR lensassembly 60, that is, the position on the line linking the center of theCR lens assembly 60 and the middle point of a side of the CR lens piece3 a on the outside that is not joined to another. The other CR lenspieces 3 b, 3 c, and 3 d are cut out of the same cylindrical R lens insuch a manner that the center positions of the respective R surfacesincreasingly deviate by 1.28 mm each from the positions including thecenter of the CR lens assembly 60 similar to the above-described indirections in which the sides on the outside extend. In other words, asshown in FIG. 7, the respective center positions of the CR lens piecesdeviate from the mechanical axis 61 passing through the center of the CRlens assembly 60 in the directions in which the sides on the outside ofthe respective lens pieces extend by 1.28 mm for the CR lens piece 3 b,2.56 mm for the piece 3 c, and 3.84 mm for the piece 3 d.

Further, the thickness of the R surface at the center of the mechanicalaxis of the CR lens pieces 3 a, 3 b, 3 c, and 3 d forming the CR lensassembly 60 is 1.0 mm each.

Here, the appearance of a case where a laser beam passes through one CRlens is shown in FIG. 9. It will be recognized that a circular laserbeam La is deformed into an elliptical laser beam Lb longer than it iswide by a cylindrical concave surface (R surface) of one face (face onthe front side) 4 a of a CR lens 4. Therefore, no matter which CR lenspiece constituting the CR lens assembly 60 the circular laser beampasses through, the laser beam becomes an elliptical laser beam longerthan it is wide as long as the curve direction of the R surface of theCR lens piece is in the vertical direction.

The CR lens assembly 60 is installed after adjustment at the time ofassembly of the module 1. The laser beam from the light emitting unit 22is ideally emitted horizontally with respect to the optical axis.However, there are subtle variations as described above, and thereforethe adjustment is different among individual laser beams.

Hence, the CR lens assembly 60 is set between the aperture 13 a of thelight emitting unit 22 and the vibration mirror 31 at a position asclose as possible to the aperture 13 a, and is rotated 90° each timearound the mechanical axis 61 so that the four CR lens pieces 3 a, 3 b,3 c, and 3 d having the respective different center positions of the Rsurfaces are selectively inserted in sequence into a laser beam passingposition, so that a CR lens piece by which variations of beams becomesmallest is selected for adjustment. When the CR lens piece 3 a isselected, the optical axis is not adjusted, and when the CR lens pieces3 b, 3 c, and 3 d are selected, the optical axis is adjusted by 1°, 2°,and 3° respectively in this example. Once set at the time of assembly,this adjustment does not need to be performed thereafter.

FIG. 10 is a schematic view when the CR lens assembly 60 is placed suchthat the R surfaces of the four CR lens pieces 3 a, 3 b, 3 c, and 3 dface in the irradiation direction of a laser beam, and one of the CRlens pieces 3 a, 3 b, 3 c, and 3 d is selected to perform optical axisadjustment of the laser beam. Where arrangement is made such that whenthe CR lens piece 3 a is selected to be at the laser beam passingposition, the center position of its R surface is on an optical axis 5,the direction of the optical axis 5 is kept horizontal and unchanged(tilt at 0°), and when the CR lens pieces 3 b, 3 c, and 3 d are selectedin sequence to be at the laser beam passing position, the centerpositions of their R surfaces are deviated upward from the optical axis5 by the distances shown in FIG. 7 respectively, whereby the horizontaloptical axis 5 tilts upward by 1°, 2°, and 3° respectively, so that theposition of a spot light at a predetermined distance from the CR lensassembly 60 varies as shown by A, B, C, and D. Further, the CR lenspiece in any case provides an elliptical laser beam longer than it iswide.

In this case, the laser beam deflecting downward (in a direction shownby an arrow A) from the horizontal optical axis 5 is corrected byselecting one of the CR lens pieces 3 b, 3 c, and 3 d, thereby allowingthe direction of emission thereof to be substantially coincident withthe horizontal optical axis 5.

FIG. 11 is a schematic view when the CR lens assembly 60 is placed withits front and rear faces reversed such that the R surfaces of the CRlens pieces 3 a, 3 b, 3 c, and 3 d face in the direction of the lightsource, and one of the CR lens pieces 3 a, 3 b, 3 c, and 3 d is selectedto perform optical axis adjustment of a laser beam. The boundary linesbetween the CR lens pieces are shown by broken lines for convenience forthe purpose of discriminating this case from that in FIG. 10.

Also in this case, when the CR lens piece 3 a is selected to be at thelaser beam passing position, the center position of its R surface is onan optical axis 5, so that the direction of the optical axis 5 is kepthorizontal and unchanged (tilt at 0°), and, in this state, when the CRlens pieces 3 b, 3 c, and 3 d are selected in sequence to be at thelaser beam passing position, the center positions of their R surfacesare deviated downward from the optical axis 5 by the distances shown inFIG. 7 respectively, whereby the horizontal optical axis 5 tiltsdownward 1°, 2°, and 3° respectively, so that the position of a spotlight at a predetermined distance from the CR lens assembly 60 varies asshown by −B, −C, and −D. Further, the CR lens piece in any case providesan elliptical laser beam longer than it is wide.

In this case, the laser beam deflecting upward (in a direction shown byan arrow B) from the horizontal optical axis 5 is corrected by selectingone of the CR lens pieces 3 b, 3 c, and 3 d, thereby allowing thedirection of emission thereof to be substantially coincident with thehorizontal optical axis 5.

FIG. 12 is a view schematically showing selection states provided by theCR lens assembly that enables selection of these seven kinds ofadjustment states. The selections states of CR lens pieces 3 a, 3 b, 3c, and 3 d when the CR lens assembly 60 is placed such that one face(front face) with each of R surfaces of the CR lens pieces 3 a, 3 b, 3c, and 3 d formed thereon faces in the irradiation direction of a laserbeam, as in FIG. 10, are shown by the respective numerals and symbols onthe lower tier. Further, the selections states of the CR lens pieces 3a, 3 b, 3 c, and 3 d when the CR lens assembly 60 is placed such thatanother face (rear face) with each of flat surfaces of the CR lenspieces 3 a, 3 b, 3 c, and 3 d formed thereon faces in the irradiationdirection of a laser beam, as in FIG. 11, are shown by the respectivenumerals and symbols on the upper tier. A CR lens piece 3 a is not shownon the upper tier because the center position of the R surface isunchangeable even if its front and rear faces are reversed.

It should be noted that the boundary lines in the CR lens pieces 3 a, 3b, 3 c, and 3 d in the CR lens assembly on the upper tier are shown bybroken lines for convenience for the purpose of discriminating them fromthose on the lower tier. Further, numerical value examples of adjustmentangles of the tilt of the optical axis at the time of selection of theCR lens pieces are shown on the upper side of the upper tier. However,the adjustment directions of the tilt of the optical axis are reversedbetween the selection states on the lower tier and the upper tier evenwhen the same CR lens piece is selected, as described above.

Next, an adjustment example of the optical axis of a laser beam actuallyemitted from the laser beam generating part 20 will be described withFIG. 13.

An arrow F1 shown in FIG. 13 shows an error direction of a chip positionof the laser diode in the light emitting unit 22, and an arrow F2 showsa positional deviation direction of the collimator lens 23.

As a result, the emission direction of a laser beam will deviate asshown by broken lines, but orientation of the CR lens assembly 60 asshown in FIG. 11, that is, selection of, for example, the CR lens piece3 c (establishment of the selection state at the middle on the uppertier in FIG. 12) allows the emission direction of the laser beam to besubstantially coincident with the horizontal optical axis 5 as shown bya solid line.

Here, various examples of the CR lens assembly will be shown in FIG. 14to FIG. 19. In these drawings, all of the CR lens assemblies are shownby numeral 6 for convenience, CR lens pieces forming them are shown bynumerals a to f, and CR lens pieces b, c, and d when front and rearfaces of the above CR lenses are reversed are shown by numerals b′, c′,and d′ respectively.

FIG. 14 is a plan view of a basic form of the CR lens assembly 6 whichis composed of four right triangular CR lens pieces a to d as in theabove-described embodiment.

A part (A) to a part (D) in FIG. 15 show changes in the direction (tiltdirection and tilt degree) of optical axes when laser beams pass throughthe center parts of the CR lens pieces a to d (including the CR lenspieces b′ to d′ when their front and rear faces are reversed).

In this case, each of the CR lens pieces a to d forming the CR lensassembly 6 has one face S1 that forms a cylindrical concave surface (Rsurface) having the same curvature and a different center position andanother face S2 that is a flat surface orthogonal to the optical axis 5.

A part (A) to a part (D) in FIG. 16 is a view, similar to the part (A)to the part (D) in FIG. 15, showing another example. The plan view ofthis example is the same as FIG. 14, but each of CR lens pieces a to dforming a CR lens assembly 6 has one face S1 that forms a cylindricalconcave surface (R surface) having the same curvature and the samecenter position as well and another face S2 that is a flat surfacetilting at a different angle to a curve direction of the cylindricalconcave surface with respect to a direction orthogonal to the opticalaxis 5.

The CR lens pieces a to d of this CR lens assembly can also change,similarly to those shown in FIG. 15, the direction of the optical axesof laser beams passing therethrough.

FIG. 17 to FIG. 19 show examples of the CR lens assembly havingdifferent plan shapes.

FIG. 17 is a plan view showing an example of a right hexagonal CR lensassembly composed of six equilateral triangular CR lens pieces a to f.Further, a right octagonal CR lens assembly can be composed of eightisosceles triangular CR lens pieces. As described above, one polygonalCR lens assembly 60 can be formed by joining four or more triangular CRlens pieces such that two sides of each one are adjacent to two sides ofothers. However, if the number of added CR lens pieces is too large, thearea per one piece is decreased to cause difficulty in adjusting theoptical axis, and therefore the illustrated examples are desirable.

FIG. 18 shows an example of a square CR lens assembly formed by joiningfour square CR lens pieces a to d such that two orthogonal sides of eachone are adjacent to two sides of others.

FIG. 19 shows an example of a square CR lens assembly formed by joiningand holding four circular CR lens pieces a to d on one plane by asupport member 6 h with a square outline. In this case, it is desirableto arrange the CR lens pieces a to d at an equal distance from theircenters to the center of the support member 6 h and at even angleintervals. It is also possible to join and hold six or eight circular CRlens pieces on one plane using a support member having an outline of aright hexagon or right octagon, thereby forming a right hexagonal orright octagonal CR lens assembly.

Both faces of each CR lens piece of each of the CR lens assemblies are acylindrical concave surface and a flat surface similar to those of eachof the CR lens pieces shown in FIG. 15 or FIG. 16.

The above-shown examples are for CR lens assemblies composed of four ormore CR lens pieces, and it is also possible to form a square CR lensassembly by joining oblique sides of two right triangular CR lenspieces, or to form a square CR lens assembly by joining long sides oftwo rectangular CR lens pieces. Further, it is also possible to form oneCR lens assembly by joining two or more circular or arbitrary planeshaped CR lens pieces.

As long as comprising at least two CR lens pieces having differentcenter positions of the R surfaces or different tilts of planes, the CRlens assembly is used with its front and rear faces reversed whennecessary, thereby allowing at least three or more kinds of optical axisadjustment states to be selected.

According to the embodiment of the invention using such CR lensassemblies, the following effects can be obtained.

(1) Each R surface (cylindrical concave surface) of the CR lens assemblywidens a laser beam passing therethrough only in the vertical directionto deform it into an ellipse longer than it is wide and not in thehorizontal direction, thereby making it possible to reduce noise causedby variations in printing or contamination and dust without changing thehigh resolution at the time of reading a bar code symbol from that by acircular laser beam that is the same in length and width. In otherwords, by widening a laser beam in the vertical direction that is thedirection of bars of the bar code symbol, the possibility of errordetection thereof can be reduced in terms of area.

(2) The area of a laser beam applied to the bar code symbol is similarlyincreased, so that optical noise caused by a spectacle pattern can bereduced. This is achieved through use of such a phenomenon that the areaof a laser beam and the optical noise are in inverse proportion. Itshould be noted that since the bar code symbol has no information in thevertical direction, vertical widening of the irradiation spot exerts noinfluence.

(3) A plurality of CR lens pieces are combined to constitute a CR lensassembly, which is used to perform optical axis adjustment of a laserbeam, and therefore the optical axis adjustment can easily be performedwithout specially providing an adjustment mechanism that is complicatedand occupies much space. Actually, the adjustment is one of only aboutseven kinds according to this embodiment using the above-described CRlens assembly composed of four CR lens pieces.

Owing to the optical axis adjustment by the CR lens assembly, thevariations in optical axes of laser beams are drastically decreased from±4° in the prior art to ±(0.5 to 1)°.

Next, the configuration and operation of the vibration mirror driver 30shown in FIG. 1 will be described in detail with reference to FIG. 20 toFIG. 22.

With a reduction in cost and size of the module for the opticalinformation reader, it is necessary to improve details of components.However, a decrease in scanning accuracy due to the reduction in sizeshould be avoided.

Although a conventional vibration mirror driver comprises a plurality ofyokes and coils, either of them is composed of a single piece, whereby areduction in space and cost can be achieved.

Besides, the movable magnet and the yoke are formed in round shapes (Rshapes) in the prior art. This makes the gap between the movable magnetand the yoke uniform at any turn position and the magnetic flux densityalso uniform. However, the components in the R shapes require mucheffort in molding and increase cost as well.

If it is possible that the movable magnet is constituted of arectangular parallelepiped sintered magnet and the yoke is constitutedof a plate-shaped yoke, they can be manufactured without much effort andreduced in size.

It has been found that when the rectangular parallelepiped sinteredmagnet and the plate-shaped yoke are in use, there exist a part of highmagnetic flux density and a part of low magnetic flux density, whichcancel each other out, resulting in a constant density as a whole.

The yoke is logically usable if it is like an infinitely small pointthrough use of its property that the magnet also rotates with itsrotation, and therefore can be reduced in size.

Fine processing performed on components necessarily increases cost. Forexample, an oil pocket of a bearing is typically made by providingseveral grooves in the axial direction, but it is desirable to employ asimple processing method that allows a mold to have a simple structurein consideration of the entire cost.

The module for the optical information reader according to the inventionis simplified in structure and reduced in size in consideration of thesepoints, and devised to attain a necessary performance.

FIG. 20 is a plan view of the vibration mirror driver, and FIG. 21 is aside view of the same. In these drawings, numeral 31 denotes thevibration mirror for scanning, numeral 32 the vibration mirror holdingmember for holding the vibration mirror 31 adhered to the front endpart, numeral 33 the movable magnet, and numeral 34 the support shaftfor turnably supporting the vibration holding member. Further, themovable magnet 33 is fixed to the lower part of the rear face of thevibration mirror holding member on the opposite side to the vibrationmirror 31 with respect to the support shaft 34.

Further, numeral 35 denotes the coil unit fixedly provided such as tooppose the movable magnet 33 with a space intervening therebetween, andis composed of the coil 36 and the thick plate-shaped yoke 37 providedthrough the coil 36 in a direction perpendicular to the windingdirection of the coil 36.

Further, the movable magnet 33 and the yoke 37 out of operation (in astate where power is not fed to the coil 36) are in the form ofstraight, parallel to each other, and the sectional area of the yoke 37in a direction orthogonal to the parallel direction is smaller than thesectional area of the movable magnet in the same direction. Twoterminals 35 a of the coil unit 35 are connected to a circuit board 70as shown in FIG. 21.

The yoke 37 of the coil unit 35 is provided through the coil 36perpendicularly to the winding direction of the coil 36 as describedabove, and is inserted into and secured to a pair of slits 16 a and 16 bformed in the sidewall part 12 and the inner wall part of the modulecasing 10 shown in FIG. 3, via the insulating member that also serves asa bobbin of the coil 36. This placement of the yoke 37, that is, theplacement of the coil unit 35 is adjusted first in consideration of amagnetic force, and they are secured to that position.

The movable magnet 33 is placed slightly spaced from the coil unit 35.The rear part of the vibration mirror 31 is joined to the movable magnet33 via the support shaft 34 that is secured perpendicularly to themodule casing.

The support shaft 34 is covered with the vibration mirror holding member(holder) 32 that also serves as a slide bearing, and loosely holds bothupper and lower faces in the axial direction of the vibration mirrorholding member 32 by sliders 38 and 39 fitted to the support shaft 34.Therefore, the vibration mirror holding member 32 is configured to befreely movable with respect to the support shaft 34 in its axialdirection within a predetermine range so as to be capable of performingvery small amplitude movement.

The sliders 38 and 39 are composed of resin washers and function toprevent contact and interference so that the vibration mirror holdingmember 32 is in a floating state. In this state, the vibration mirror 31is vibrated in a seesaw manner about the support shaft 34 by thefunction of electromagnetic induction by the coil unit 35 and themovable magnet 33.

Further, the vibration mirror holding member 32 is provided with abearing hole 32 a as shown in FIG. 22 to form a slide bearing structure.Further, the bearing hole 32 a is formed to have a diameter at the innermiddle part slightly larger than the diameter at both end parts so thatthe middle part gradually expands. This middle part forms an oil pocket32 b between the part and the support shaft 34 to be capable of storingsilicon oil for lubricating the interface between the vibration mirrorholding member 32 and the support shaft 34.

Next, simulations will be performed on changes in magnetism around themovable magnet 33 and the yoke 37 in the vibration mirror driver 30having the above-described structure. FIG. 23 to FIG. 25 showsimulations when the movable magnets 33 are rotated with the yokes 37not moved.

FIG. 23 shows a state where the movable magnet 33 stands still. Themagnetic flux density is distributed in a manner to become lower as itgoes farther with a part where the movable magnet 33 and the yoke 37 areclosest to each other as a center. The part of high magnetic fluxdensity and the part of low magnetic flux density cancel each other outin this state, resulting in a constant magnetic flux density as a whole.

FIG. 24 shows a case in which the movable magnet 33 is rotated 13.5° tothe left in the drawing. Unlike the above-described standing stillstate, the magnetic flux density is uniformly distributed around theyoke 37. The rotation of the movable magnet 33 causes one edge a of aface opposing the yoke 37 to become distant from the yoke 37 and anotheredge b to come close to the yoke 37. Naturally, the magnetic fluxdensity around the one edge a which has become distant becomes lower,and the magnetic flux density around the other edge b which has comeclose becomes higher. However, the low part and the high part canceleach other out even though the magnet 33 is rotated, resulting in aconstant magnetic flux density as a whole.

FIG. 25 shows a case in which the movable magnet 33 is rotated −13.5° tothe right in the drawing. The rotation direction is opposite to that ofthe case in FIG. 24, and therefore one edge a of the movable magnet 33comes close to the yoke 37 and another edge b becomes distant from theyoke 37. In this case, the distribution of the magnetic flux densitybecomes like the distribution in FIG. 24 vertically reversed, resultingin a constant magnetic flux density as a whole also in this case.Accordingly, the vibration mirror 31 can always be turned right and leftwith a constant magnetic flux density.

FIG. 26 is a diagram showing waveforms of a timing signal for turningthe vibration mirror 31 right and left and a current fed through thecoil 36. A part (a) shows the turn direction of the vibration mirror 31,a part (b) shows the waveform of the timing signal, and a part (c) showsthe coil current.

The waveform of the timing signal is a rectangular wave that reversesevery 10 msec, and a current of 10 mA to 20 mA with a pulse width of 1msec to 2 msec is fed, as the coil current, alternately in oppositedirections every rising time and falling time of the timing signal.

The vibration mirror driver is characterized in the following points.

-   (1) In the coil unit 35, the yoke 37 is provided through the coil 36    in the direction perpendicular to the winding direction thereof.-   (2) The movable magnet 33 and the yoke 37 are formed not in round    shape but flat.-   (3) The transverse section of the yoke 37 is made smaller than the    transverse section of the movable magnet 33.-   (4) The vibration mirror holding member 32 is made slidable in the    axial direction of the support shaft 34.-   (5) The oil pocket 32 b is formed by increasing the diameter of the    middle part of the bearing hole 32 a of the vibration mirror holding    member 32.

With this vibration mirror driver, the following effects can beobtained.

-   (1) The yoke 37 is secured, provided through the coil unit 35 in the    direction perpendicular to the winding direction of the coil 36,    whereby the number of members can be reduced.-   (2) The magnet and the yoke, which are formed in R shape (round    shape) in the prior art, are formed in flat shape such as a    rectangular parallelepiped or a straight rod, whereby the space in    the module can be reduced to realize a reduced size module, leading    to reduced cost.-   (3) The yoke is reduced in size, whereby the weight of the driver    part can be reduced. Further, the size of the transverse section of    the yoke is made smaller than the transverse section of the movable    magnet, thereby providing improvement in positioning accuracy due to    magnetic levitation.-   (4) The vibration mirror holding member 32 and the vibration mirror    31 and movable magnet 33 which are integrated therewith are made    slidable in the axial direction of the support shaft 34 and kept in    a floating state, whereby they have little resistance at the time of    turn and thus can be smoothly turned by a small driving force, so    that the movable magnet 33 and the coil unit 35 can be further    reduced in size as well as save in power consumption.-   (5) The oil pocket of the bearing part is formed to have a gently    curved cross section, resulting in a simple structure and can be    produced at low cost.

The shield effect of an electronic circuit, especially, an LSI in themodule for the optical information reader will be described here.

As described above with FIG. 4, in this module for the opticalinformation reader according to the invention, when the circuit board 70which conducts signal processing and various controls is screwed to thetop face of the module casing 10 while also serving as the top cover,the LSI 71 mounted on the circuit board 70 is accommodated in the LSIaccommodating recessed part 14 of the metal module casing 10 to beshielded with a metal face at the periphery. Further, if the layer wherethe wiring layer of the circuit board 70 is formed into a shield layer,the top face of the LSI 71 can also be shielded.

Therefore, the LSI 71 is substantially sealed by the metal box of themodule casing 10 and the shield layer of the circuit board 70, into adesirable state. This can prevent influence of electromagnetic wavenoise generated by other electronic equipment, mobile phone, and so on.

FIG. 27 and FIG. 28 show simulation waveforms when an electromagneticwave noise at about 30 KHz is superimposed, FIG. 27 showing a waveformof a detection signal in a case of using the module according to theembodiment of the invention and FIG. 28 showing a waveform of adetection signal in a case of using a conventional module in which anLSI is placed on the top face of a circuit board, respectively. The partwhere the amplitude of the waveform greatly varies is a part for readinga bar code symbol.

As is clear from comparison between FIG. 27 and FIG. 28, anelectromagnetic wave noise of about 0.3 Vpp is superimposed on thewaveform in FIG. 28. On the waveform in FIG. 27, the amplitude of thenoise is very small. This shows that the influence of the noise can beavoided by the above-described embodiment of the invention.

FIG. 29 and FIG. 30 show simulation waveforms when a mobile phone isused near the module, FIG. 29 showing a waveform of a detection signalin a case of using the module according to the embodiment of theinvention and FIG. 30 showing a waveform of a detection signal in a caseof using the conventional module in which the LSI is placed on the topface of the circuit board, respectively.

In comparison between the simulation results, an electromagnetic wavenoise of about 0.3 Vpp due to the influence of the mobile phone issuperimposed in the case of the conventional device shown in FIG. 30,whereas the noise is very little in the case of the device of theinvention shown in FIG. 29. This shows that according to theabove-described embodiment of the invention, even though a strongelectromagnetic wave such as from a mobile phone occurs, the noise canbe substantially reduced so that information such as a bar code symbolcan be accurately read at all times.

INDUSTRIAL APPLICABILITY

As has been described, according to the invention, it is possible tomodularize the primary part of the optical information reader of thelight beam scanning type, simplify the structures of attachment parts ofthe light emitting unit and the collimator lens, and enable read withhigh accuracy, so as to realize a reduction in size and price of theoptical information reader.

Further, the optical axis adjustment of a laser beam is facilitated, andmost of the variation with time and the influence of optical noise orelectromagnetic wave noise are eliminated, thus enabling informationread with high accuracy for a long time.

1. A module for an optical information reader in which at least a lightemitting unit with a laser diode as a light source, a collimator lens, avibration mirror for scanning, a condensing mirror or a condensing lens,and a light receiving unit are installed in a module casing formodularization, wherein a cylindrical lens assembly comprising aplurality of cylindrical lens pieces integrally joined is providedbetween said light emitting unit and said vibration mirror, wherein eachof said plurality of cylindrical lens pieces has one face that forms acylindrical concave surface having the same curvature and a differentcenter position and another face that is a flat surface orthogonal to anoptical axis, and wherein one of said plurality of cylindrical lenspieces is selected and inserted into a passing position of a laser beamgenerated by said light emitting unit to enable adjustment of an opticalaxis of the laser beam.
 2. The module for an optical information readeraccording to claim 1, wherein said plurality of cylindrical lens piecesare four or more triangular cylindrical lens pieces and are joined suchthat two sides of each of said cylindrical lens pieces are adjacent totwo sides of other said cylindrical lens pieces to form said cylindricallens assembly in one polygon.
 3. The module for an optical informationreader according to claim 1, wherein said plurality of cylindrical lenspieces are four square cylindrical lens pieces and are joined such thattwo orthogonal sides of each of said cylindrical lens pieces areadjacent to two sides of other said cylindrical lens pieces to form saidcylindrical lens assembly in one square.
 4. The module for an opticalinformation reader according to claim 1, wherein each of said pluralityof cylindrical lens pieces is a circular cylindrical lens piece, andsaid cylindrical lens pieces are joined and held on one plane using asupport member to form said one cylindrical lens assembly.
 5. The modulefor an optical information reader according to claim 1, wherein saidmodule casing is made of metal and formed with an LSI accommodatingrecessed part, and wherein a circuit board with a shield layer and anLSI mounted thereon for forming a circuit for signal processing andcontrol is attached to an open face of said module casing with the LSIaccommodated in said LSI accommodating recessed part, and the LSI isshielded with a metal face of said module casing and the shield layer ofthe circuit board.
 6. A module for an optical information reader inwhich at least a light emitting unit with a laser diode as a lightsource, a collimator lens, a vibration mirror for scanning, a condensingmirror or a condensing lens, and a light receiving unit are installed ina module casing for modularization, wherein a cylindrical lens assemblycomprising a plurality of cylindrical lens pieces integrally joined isprovided between said light emitting unit and said vibration mirror,wherein each of said plurality of cylindrical lens pieces has one facethat forms a cylindrical concave surface having the same curvature andthe same center position and another face that is a flat surface tiltingat a different angle to a curve direction of the cylindrical concavesurface with respect to a direction orthogonal to an optical axis, andwherein one of said plurality of cylindrical lens pieces is selected andinserted into a passing position of a laser beam generated by said lightemitting unit to enable adjustment of an optical axis of the laser beam.7. The module for an optical information reader according to claim 6,wherein said plurality of cylindrical lens pieces are four or moretriangular cylindrical lens pieces and are joined such that two sides ofeach of said cylindrical lens pieces are adjacent to two sides of othersaid cylindrical lens pieces to form said cylindrical lens assembly inone polygon.
 8. The module for an optical information reader accordingto claim 6, wherein said plurality of cylindrical lens pieces are foursquare cylindrical lens pieces and are joined such that two orthogonalsides of each of said cylindrical lens pieces are adjacent to two sidesof other said cylindrical lens pieces to form said cylindrical lensassembly in one square.
 9. The module for an optical information readeraccording to claim 6, wherein each of said plurality of cylindrical lenspieces is a circular cylindrical lens piece, and said cylindrical lenspieces are joined and held on one plane using a support member to formsaid one cylindrical lens assembly.
 10. The module for an opticalinformation reader according to claim 6, wherein said module casing ismade of metal and formed with an LSI accommodating recessed part, andwherein a circuit board with a shield layer and an LSI mounted thereonfor forming a circuit for signal processing and control is attached toan open face of said module casing with the LSI accommodated in said LSIaccommodating recessed part, and the LSI is shielded with a metal faceof said module casing and the shield layer of the circuit board.